COMECO RT28U User manual

COMECO Inc., P.O.Box 378, Plovdiv 4000, BULGARIA, tel: [phone], 646524, fax: 634089
e-mail: [email protected]g, WWW.COMECOGROUP.COM
RT28U
with rotary encoder
OPERATION MANUAL
Please, read this Operation Manual before mounting and operating.
Save the Manual for future references.
PROGRAMMABLE CONTROLLER
v5-2-08.14

Overview 2
RT28U is a low-cost multifunctional
programmable controller. Its universal
input accepts the most common RTDs,
thermocouples, and linear signals.
The device can be equipped with up to 2
relay outputs, which can control various
actuators using ON/OFF control algorithm,
and the optional RS485 interface enables
networking. RT28U allows adjusting
of the built-in digital filters
and the programmable output delay,
resulting in increased operation reliability
in case of industrial interferences.
Input Setting
Input type Short out
0...10 V J2
all the rest J1
♦Open the case.
♦Follow the diagram on the left
to find the configuration jumpers
J1 and J2, located on the main board.
♦To set the desired input type,
short out the respective
configuration jumper.

Mounting 3
♦Place RT28U
into a 90 x 90 mm (for case 'B'),
90 x 42 mm (for case 'H'), or
42 x 90 mm (for case 'V') panel cut-out.
♦Tighten it into place using the enclosed
mounting brackets.
Electro-Magnetic Interference (EMI) Issues
Important note:
A built-in RC noise
suppression circuit may
be connected in parallel
with relay contacts.
Full AC voltage isolation
may NOT be provided
when relay contacts
are open.
Small AC current
(≈1.5 mA at 230 VAC)
may still flow through
the RC circuit.
♦All signal wires must be shielded.
They must not be packaged together
with power cables.
♦Never lay the signal wires close
to inductive or capacitive noise sources,
such as relays, contactors, motors, etc.
♦All shields have to be grounded ONLY
at one end, as closer as possible
to the controller terminals.
♦Avoid sharing supply lines with powerful
consumers, especially with inductive loads,
switched on and off.
♦To stop unwelcome interference signals
entering through the power supply lines,
use shielded 1:1 isolation transformer.
♦Shunt all switched (not only those switched
by the controller) inductive consumers
with special suppression networks:
RC group and varistor - for AC loads,
or diode - for DC loads.
♦If the controller operates in a very powerful
EMI area, it has to be mounted inside
a grounded metal shielding box.
♦To protect the interface
from electro-magnetic disturbances,
follow the RS485 standard guidelines.

Wiring 4
Important notes:
♦Power supply must be turned off
during mounting and wiring.
♦In case of 90...250 V power supply,
grounding the device through terminal A2
is mandatory for covering safety standards.
♦Strictly observe the requirements
for RS485 network building.
Input signal wiring
Connect the input
with regard to its type
through the respective terminals
on the device back.
Voltage transmitters
should be powered ONLY
by external source.
Output wiring
Connect the outputs
with regard to their types
(see 'Specifications')
via the respective terminals.
RS485 wiring
Connect the unit
to the RS485 network line
via the respective
and depending on the case type
(see 'Specifications') terminals.
Power supply wiring
Connect the right power
supply voltage for your device
(see 'Specifications')
through the respective terminals.
More detailed
wiring schematics
are available at
comecogroup.com
under 'Support' tab.

Parameter Programming 5
Some parameters
are accessible only
when the respective
functionality is installed.
(see 'Specifications').
- Changing
Point Position value
reflects on the real value
of all parameters
with ISU.
E.g.: changing
Point Position value
from (0) to (0.0)
would change
a set-point value
of 100 to 10.0.
Device parameters
RT28U is a programmable device whose
service behavior is determined by a set
of parameters. All the parameters, along
with their names, symbols, and value ranges,
are given in Table 1.
The parameters and their values are listed
in the order they appear on the display
when the encoder knob is being turned UP.
Setting numerical parameter value
♦Enter parameter value adjustment mode
(see 'Program Levels').
♦The whole part of the value together with
the left zeroes appears on the display,
and all digits blink.
♦To increase or decrease the value,
turn the encoder knob respectively
UP or DOWN.
♦For fine adjustment, turn the encoder slowly
as to sense its positions. For coarse
adjustment, turn the encoder curtly.
♦Confirm the adjusted value by pressing
the encoder knob.
♦If the new value has not been confirmed
and the encoder has not been used
for a certain period of time,
value adjustment automatically ceases,
and the parameter retains its initial value.
Setting symbolic parameter value
♦Enter parameter value adjustment mode
(see 'Program Levels').
♦Read the blinking parameter value.
♦To change the current value,
turn the encoder UP or DOWN.
♦Confirm the adjusted value by pressing
the encoder knob.
♦If the new value has not been confirmed
and the encoder has not been used
for a certain period of time,
value adjustment automatically ceases,
and the parameter retains its initial value.

Parameter Symbol Description
Parameters of Level L3
Input Type inP Type of signal that can be connected to the device input
Unit Uni Temperature measurement unit
Point Position 
Pnt Display decimal point position
Input Low ILo Display value at low limit of the linear input range
Input High IHi Display value at high limit of the linear input range
Input Correction ICr Constant to be added to the measured input value
Address Adr Device address
Baud Rate bAu Serial interface rate
Gradient Grd Maximum admissible input change for 120 ms sampling period
Filter Time \t Relative time constant of the input filter
Filter Band \b Zone around the measured value, within which the filter is active
SP Limit Low %[L Set-point low limit
SP Limit High %[H Set-point high limit
Direction 1 dR1 Control action direction of output K1
Direction 2 dR2 Control action direction of output K2
Parameters of Level L2
+Differential 1 [e1 Relay switching differential over set point for output K1
-Differential 1 me1 Relay switching differential under set point for output K1
Time On 1 ym1 ON duration of pulsed output K1
Time Off 1 y\1 OFF duration of pulsed output K1
Hold 1 Hl1 Holds the output K1 reaction
The same 5 parameters, but with index 2– for output K2
Parameters of Level L1
Set Point 1 %[1 Set-point value of output K1
Set Point 2 %[2 Set-point value of output K2

Table 1
Value Unit Notes
Pyh, Pyt - Pt100: -100…850 °C, Pt1000: -100…600 °C
Px1,Px2 - PTC 1k: -50...150 °C, PTC 2k: -50...150 °C
R)1 - resistive linear: 0…1 kΩ
yxb - T/C "B": 200...999 °C
yxJ - T/C "J": -20...999 °C
yx" - T/C "K": -20...999 °C
yxr - T/C "R": 0...999 °C
yxS - T/C "S": 0...999 °C
yxt - T/C "T": -40...400 °C
u- voltage linear: 0…100 mV
I0, I4 - current linear: 0…20 mA, 4…20 mA
w10 - voltage linear: 0…10 V
.C, .F - °C, °F
0, 0.0, 0.00 - when indicating values with the input-signal measurement unit (ISU)
-199 ... 999 ISU These parameters make sense ONLY in case of a linear input signal.
-199 ... 999 ISU display offset value
1…254 -
!2, @4, $8, (6 bps 1200, 2400, 4800 (factory-set), 9600 bps
0 … 999 ISU used for input peak filtration; value '0' cancels the filtration
0 … 999 - This parameter and the following one define a low-pass input filter.
0 … MISU temperature: whole part of M≤100; linear: M= 25% of input range
within input range ISU These parameters keep the set points in safe limits,
preserving them from random changes.
coo, hEA - 'cooling' - activates over set point, 'heating' - activates under set point
0 ... 999 ISU less than (high range limit - Set Point 1)
0 ... 999 ISU less than (Set Point 1 - low range limit)
0 ... 999 sec. pulse duration; value '0' disables pulse mode
0 ... 999 sec. pause duration; value '0' disables pulse mode
0 ... 999 sec. Value '0' disables hold mode.
-199 ... 999 ISU within range SP Limit Low ... SP Limit High

Program Levels 8
Basic level
At power-on, RT28U enters Basic level.
At this level, the device indicates
the measured input value (PV)
with a resolution, according to
the Point Position parameter.
♦If the whole part of PV cannot be
entirely displayed, the unit generates
a blinking 'overflow' message
(oL or -oL, depending on PV sign).
♦If PV is out of its operating range
(the input range according
to Table 1, extended by 5%
on both sides), the device displays
blinking symbolic message:
<_> (under-range) or
{+} (over-range).
When PV is out of physical range,
the unit displays ---.
♦Upon entering Basic level, RT28U
may display the ini message,
indicating that some time is necessary
for filter initialization.
♦The noi message may appear
as a result of the peak filter operation
(see 'Input filtration').
Set-point adjustment (Level L1)
♦To enter Set Point 1 adjustment mode,
press, hold, and turn UP
the encoder knob until %[1 appears
on the display. Release the knob
to view the set-point value.
♦To enter Set Point 2 adjustment mode,
follow the same procedure,
but turn the encoder DOWN.

Program Levels 9
Programming (Levels L2 and L3)
♦Enter from Basic level by pressing
and holding (without turning)
the encoder knob.
♦To access and adjust the parameters
from level L2, release the knob
while PAr is displayed.
To enter level L3, release the knob
when C0n appears on the display.
♦Choose a parameter by rotating
the encoder. Turn the knob slowly
so not to skip parameters.
♦To enter parameter value adjustment
mode, press the encoder knob.
♦If the encoder has not been used
for a while, the device automatically
returns to Basic level, storing all
confirmed changes.
♦For quick exiting and saving,
select the rtn parameter
and press the encoder knob .
Output Control
Control output operation
♦The control outputs operate according
to the control algorithm parameters.
♦The outputs deactivate
with the value change
of one of the following configuration
parameters - Point Position,Input Low,
Input High, and Input Correction -
and remain inactive till Basic level
is entered.
♦The outputs deactivate also
when an error has been detected
(see 'Error messaging')
and remain inactive until all
discrepancies are resolved
and programming exited.
♦An input failure
deactivates the outputs too.

Output Control 10
ON/OFF control algorithm
The static characteristic
of a relay controlled
by an ON/OFF algorithm
is shown on the left drawing.
Output hold
For eliminating undesirable
output switches, additional
parameter (Hold) is assigned
to hold the output reaction
for certain period of time.
Output pulse mode
When an output is activated
by the control algorithm,
it can either stay ON or pulse
depending on Time On and
Time Off parameter values.

Input Filtration 11
Peak filter
This filter is intended for eliminating
pulse spikes (peaks), which can appear
in the input signal, in the following way:
♦RT28U measures the input signal value
every 120 ms (sample time).
♦The measured values are compared
subsequently. The filter checks
the difference between the last
2 samples. If it does not exceed
Gradient value, the device accepts
the signal as normal.
♦If the last measured value differs
from the previous one by more than
the Gradient value, the filter output
is held until the device determines
a presence of a normal signal.
It is possible only if the input signal
has not been changed with more than
the Gradient value for 4 subsequent
samples.
♦If the device has not determined
a normal signal for 20 subsequent
samples, noi appears on the display
(see 'Basic level').
Low-pass filter
This first-order filter acts ONLY within
a certain band around filter output value.
This has been designed to cut periodic
noises outside the communication signal
spectrum.
♦Filter operation is defined by two
parameters:
Filter Time (defines filter time constant) and
Filter Band (defines filter active band
around filter output value).
♦If the newly measured value differs
from the filter output by more than
Filter Band, the filter resets
with a new initial output value
(newly measured value).

Error Messaging 12
Message Parameters Error type
FAL all incorrect memory
br" - service required
W01 Grd out of range
W02 \t out of range
W03 \b out of range
W04 %[L out of range
W05 %[H out of range
W06 %[L,%[H %[L> %[H
W11, W21 ym1,ym2 out of range
W12, W22 y\1, y\2 out of range
W13, W23 Hl1,Hl2 out of range
W14, W24 [e1,[e2 out of range
W15, W25 me1,me2 out of range
W16, W26 %[1,%[2 outside %[L...%[H
W17, W27 %[x-mexunder input range
W18, W28 %[x +[exover input range
W29 Adr out of range
♦In some cases, RT28U
finds discrepancies
in parameter values
that must be resolved
before operating
at Basic level.
♦The device indicates
such kind of problems
by displaying
error messages
as given on the left.
♦If FAL appears
on the display,
try debugging
by turning
the power off/on.
♦If the problem persists,
press and hold
the encoder knob
(without turning) or
send command error 0
via the communication
interface to restore
the default (factory)
settings.

Communication Protocol 13
Table 2
Parameter Symbol Value
Input Type inp
pt100, pt1000,
ptc1, ptc2,
r.0.1k,
t.c.b, t.c.j,
t.c.k, t.c.r,
t.c.s, t.c.t,
u, u.0.10,
i.0.20, i.4.20
Unit unit c, f
Point Position pnt 0, 1, 2
Input Low i.hi -199...999
Input High i.lo -199...999
Input Correction i.cor
-199...999
Address addr 1...254
Baud Rate baud 1200, 2400,
4800, 9600
Gradient grad 0...999
Filter Time f.t 0...999
Filter Band f.b 0...M
Input Value p.v *
Error Info error **
* Input Value (read-only)
numerical value with ISU - measured input value
sat.lo
- ADC under-range
sat.hi
- ADC over-range
inp.br
- sensor break
break
- device failure
noise
- noisy measurement
** Error Info
0- initializes non-volatile memory
-1 - error FAL (read-only)
1...29 - errors W01... W29 (read-only)
Protocol architecture
♦The protocol is based
on UART protocol with:
Baud Rate - as defined
by parameter Baud Rate;
Data bits - 8;
Parity Control - Even;
Stop bit - 1.
♦ASCII protocol is used
for communicating,
and the information
is exchanged in frames.
♦Each frame consists of 1,
or 2 words separated
by byte 32 (SPACE),
and ends with bytes 13 (CR)
and 10 (LF). The first word
in the frame denotes
the parameter 'Symbol'
as taken from Table 2 and
the second word (if needed)
is the parameter 'Value',
both spelled with only
small Latin letters, digits,
dots, and/or the '-' sign.
Device activating
♦To respond to commands,
the device should be active.
♦For a device to be activated,
it must receive a Uхcommand,
where 'х' is the value
of the parameter Address
or the value '255' (if device
address is unknown),
and respond to it with ok..
♦If a device does not respond
even to U255, check
the UART protocol settings,
chiefly Baud Rate value.

Communication Protocol 14
Notes:
♦RT28U adds 3 spaces
in the beginning of the response.
♦RT28U returns decimal point
even when the value is integer.
♦#13 (CR) is byte 0x0D;
#10 (LF) is byte 0x0A.
♦The U255 command should be used
only in case just 1 slave is presented.
Protocol examples:
PC or other device: RT28U response:
activating device number 10
U10#13#10 ok.#13#10
reading filter time
f.t#13#10 f.t 0015.#13#10
writing filter time of 30
f.t 30#13#10 f.t 0030.#13#10
reading input value of 27.5
p.v#13#10 p.v 027.5#13#10
invalid command.
command not recognized
parity error. parity error detected
not a number. attempt to write symbols
for numerical parameter
point error. value resolution greater
than parameter’s one
out of range. value out of range
unit is busy. writing is allowed only
to device at Basic level
read only. parameter is read-only
can't save. problem with writing
in non-volatile memory
♦The device remains active
until it receives another Uх
command, but with different
device address, a FAL
error, or with reset.
♦Any Baud Rate value change
through the communication
interface also deactivates
the device.
Reading from a device
♦If the frame consists of
only 1 word, it is recognized
as a command for reading.
♦The device responds to it by
returning the same word and
its value, according to Table 2.
Writing in a device
♦If the frame consists of
2 words, it is recognized
as a command for writing.
♦With writing, transferred
are the same 2 words
that would have been
received at the respective
command for reading
from the device.
♦After successful writing,
the device responds with
the respective command
for reading, except for
the baud command.
Other device responses
♦When Error Info value is -1,
the device substitutes any
command for error reading.
♦RT28U responses in case
of incorrect protocol use
are given on the left.
Reset
To reset the device,
send command reset.

Declaration of Conformity 15
The undersigned hereby declares,
on behalf of COMECO Inc., that this
programmable controller model RT28U
has been manufactured in compliance
with standards EN 61010-1 and EN 61326-1,
and meets the requirements
of Directives 2004/108/EC and 2006/95/EC.
Krasimir Darakchiev, CEO
COMECO Inc.
Waste Disposal
Do not dispose of
electronic devices
together with
household waste
material!
If disposed of within European Union,
this product should be treated
and recycled in accordance with the laws
of your jurisdiction implementing
Directive 2012/19/EU on waste electrical
and electronic equipment (WEEE).

Specifications 16
Case
Input
Outputs:
Electromechanical relay
SSR
MOS gate
Output for external SSR
- K1
- K2
Serial Interface
Power Supply
Excitation Voltage (Vaux)
Consumption
Measurement Error
Temperature Drift
RTD Line Error
Cold-junction Error
Ambient Temperature / Humidity
Protection Class: front / terminals
'B', 'H', 'V'
programmable
up to 2
5A/250VAC with NO/NC contact
1A/250VAC
0.1A/60V, optically isolated
5...24 VDC, 30 mA
relay, SSR, MOS gate, for ext. SSR
relay, SSR, MOS gate, for ext. SSR
RS485, isolated,
RS485 for "PolyMonitor", isolated
230 VAC, 90…250 V,
24 VDC, 12...24 V,
.............................................
10...30 V, 30 mA, 24 VDC, 30 mA,
.............................................
less than 3 VA
≤±0.3% from span
≤±0.02% from span for 1 °C
≤±0.001%/Ωat Rlin. ≤50 Ω
≤±1 °C at air temperature -10…80 °C
-10…65 °C / 0…85% RH, non-condensing
IP65, IP54 / IP20
Warranty and Support
………………………….
serial number
………………………….
manufacturing date
QC check mark …….……(passed)
(stamp)
88 Slavyanska Str.
P.O.Box 378
Plovdiv 4000, BULGARIA
tel: [phone], 646524
fax: [phone], 646517
e-mail: [e-mail]
QD-8.2.4-WC
Warranty
COMECO warrants this product
to be free from defects in materials
and workmanship for 2 years. If your unit
is found to be defective within that time,
we will promptly repair or replace it.
This warranty does not cover accidental
damage, wear or tear, or consequential
or incidental loss. This warranty
does not cover any defects caused
by wrong transportation, storage, installation,
or operating (see 'Specifications').
Technical support
In the unlikely event that you encounter
a problem with your COMECO device,
please call your local dealer or contact
directly our support team.